The output voltage capability of PWM (pulse width modulated) amplifiers is ultimately limited by the availability of power transistors of requisite voltage rating. To overcome this limitation, numerous power converter architectures have been proposed that place two or more transistors in a series circuit connection such that the transistor voltage ratings become additive. One such architectural family of power converters is known as multi-level converters. Multi-level power converters are known. In the multi-level converter, the output transistors are placed directly in series across a DC power supply comprising two or more independently powered DC power supplies with output voltages commensurate with the voltage rating of the individual output transistors.
One type of multi-level converter is the diode-clamped multi-level converter (DCMLC). This circuit topology uses series arrangements of diodes and capacitors to establish the intermediate node voltages for the DCMLC. Such converters are well known. U.S. Pat. No. 6,031,738 describes and illustrates such a converter and is incorporated herein by reference in its entirety.